Unsure what is wrong...

So, I'm rather new to C, and as part of a lab homework we are supposed to read a list of numbers from a file and sort them in either ascending or descending order (user gets to choose). After doing some internet searching I decided to use a bubble sort (I can actually understand the code for the most part). However, when I compile and run, now matter what number I put in for sort_m (see code below), it always sorts it in ascending order. So:

• I assume I am misusing the if/else if/else statements, but I'm lost as to the specifics, can anyone tell me what I'm doing wrong? [FIXED]
  
• When doing the bubble sort, what is "for(x = 0; x < count; x++)" (again see below for code) used for?
  
• When I don't have "#include <stdlib.h>", I get the warning "incompatible implicit declaration of built-in function ‘exit’ ", but with it I do not, why is this?

Code:

#include <stdio.h>
#include <stdlib.h>
#define MAX 100

main() {

  /* Declare main program variables */
  char filename_i[256];                     /* Declare character filename_i, 256 characters max */
  char filename_o[256];                     /* Declare character filename_o, 256 characters max */
  int sort_m;                               /* Declare integer sort_m */
  FILE *in_fd,*out_fd;                      /* Declare the variables you will call the input & output files */
  int count,x,y,z,temp_a,temp_d;            /* Declare count,i,x,temp_a,temp_d as integers */
  count = x = y = z = temp_a = temp_d = 0;  /* Intialize all the previously declared integers at 0 */
  int array_s[MAX];                         /* Declare array_s, 100 integers max */
  int next_number;                          /* Declare integer next_number */

  /* Get name of input file from user */
  printf("Enter input file name: ");
  scanf("%s",filename_i);

  /* Open file, if it fails, print error message and exit */
  if ((in_fd = fopen(filename_i,"r")) == 0) {
    fprintf(stderr,"%s: No such file.\n",filename_i);
    exit(0);
    }

  /* This will read the numbers from the file until it reaches */
  /* end of file.  As it does this, it rights them to an array */
  while(fscanf(in_fd,"%d\n",&next_number)!=EOF){
    /* Now, we write the number we are currently reading from the file into an array */
    array_s[count] = next_number;
    count++;  /* Increase variable count by 1 */
    }

  /* Get sorting method from user */
  printf("Sort [1] Ascending or [2] Descending?\nSort Method: ");
  scanf("%d",&sort_m);

  /* Now for the sorting algorithm */
  if(sort_m = 1){
    for(x = 0; x < count; x++)
      for(y = 0; y < count-1; y++)
        if(array_s[y] > array_s[y+1]){
          temp_a = array_s[y];        /* Write array_s[y] to another variable temporarily */
          array_s[y] = array_s[y+1];  /* Overwrite array_s[y] with the smaller value, array_s[y+1] */
          array_s[y+1] = temp_a;      /* Overwrite array_s[y+1] with the larger value you temporarily stored in temp_a  */
        }
  }
  else if(sort_m = 2){
    for(x = 0; x < count; x++)
      for(y = 0; y < count-1; y++)
        if(array_s[y] < array_s[y+1]){
          temp_d = array_s[y];        /* Write array_s[y] to another variable temporarily */
          array_s[y] = array_s[y+1];  /* Overwrite array_s[y] with the larger value, array_s[y+1] */
          array_s[y+1] = temp_d;      /* Overwrite array_s[y+1] with the smaller value you temporarily stored in temp_d  */
        }
  }
  else{
    printf("Invalid selection, please run the program again");  /* Print an error message if there was no valid choice */
  }

  for(z = 0; z < count; z++){
    printf("%d\n",array_s[z]);  /* Print the array so you can see if it worked */
  }

}

Edit - Sorry for not making my title descriptive, completely slipped my mind.

Just change these lines ,

Code:

 
 if(sort_m = 1){
  to
if(sort_m == 1){ // Use == for comparison

and

Code:

 if(sort_m = 1){
  to
if(sort_m == 1){ // Use == for comparison

Use == is for comparison and = for assignment .Try to use functions in your code.

Originally Posted by karthigayan

Just change these lines ,

[stuff]

Use == is for comparison and = for assignment .Try to use functions in your code.

Okay thank you, and for your explanation too!